In these studies we propose to extract an anti-insulin peptide from the urine of patients with lipoatrophic diabetes mellitus. This peptide shall be characterized by its amino acid composition and sequence as well as biologically in dispersed fat cells and thymocytes in order to ascertain what role it may have in human diabetes mellitus or in the subcategory of completed lipoatrophy and insulin-resistant diabetes mellitus. We further propose to prepare and validate a radioimmunoassay for this biologically active substance in order to determine if it has a physiologic role or a pathologic role in the human disease, diabetes mellitus.